1. Field of the Invention
The present invention relates generally to mesoporous silica and a preparation method thereof. More particularly, the present invention relates to granular silica having mesopores and a preparation method thereof.
2. Description of the Related Art
Granular activated carbon has the superior adsorption property, persistency and economical efficiency, so the granular activated carbon has been mainly used as an adsorbent in a conventional water treatment system to remove pollutants in water. However, with the global urbanization and industrialization, new pollutants, such as heavy metals and endocrine disrupting chemicals, have appeared, so the pollutants may not be effectively removed by using the conventional water treatment system.
In this regard, mesoporous materials have been spotlighted as a substitute for the adsorbent of the granular activated carbon. In addition, various studies and research have been actively performed with respect to mesoporous silica, mesoporous carbon, and mesoporous metal oxide.
Among them, the mesoporous silica has the regular porous structure, the large specific surface area, and the wide pore size and is stable under the high temperature of about 850° C., so the mesoporous silica is generally known as to be readily reproduced (Zhao et al., 1998). The mesoporous silica is classified as MCM-41, MCM-48 and SBA-15 (Kresge et al., 1992; Zhao et al., 1998) and a study has been performed to adsorb and remove various water pollutants, such as cyanuric acid, p-chlorophenol (Copper et al., 1999) and phenol (Burleigh et al., 2002) by using the mesoporous silica.
However, although the mesoporous silica has the superior porous characteristics and adsorption property, if the powdered adsorbent is used in the water treatment process or the air pollutant treatment process, the treatment efficiency may be lowered due to the long-time exposure of the powdered adsorbent. In addition, since the powdered adsorbent has a small grain size, the powdered adsorbent may be lost during the pollutant treatment process, so the recovery of the powdered adsorbent is difficult.
For this reason, various studies and research have been pursued to granulize the powdered adsorbent. For instance, according to the study of Govindasamy et al., 2009, bentonite, methylcellulose, and tetraethyl orthosilicate (TEOS) are injected into the mesoporous silica to granulize the mesoporous silica. In addition, according to another study of Pavel et al., 2011, the granulation is achieved by using colloidal silica, and the porous characteristic and the mechanical strength of the granular silica are analyzed and measured.
However, according to the conventional method for preparing spherical molded articles or the conventional granulation method, a greater amount of organic binder or inorganic binder must be used to hold the molded article, so the purity of the molded article may be reduced. Especially, due the binder used to granulize the mesoporous materials, pores of the mesoporous materials may be occluded. In this case, the porous characteristic of the adsorbent may be degraded, so the adsorbent may not sufficiently perform the function thereof.
Therefore, it is necessary to develop the preparation method for a granular silica molded article, which can hold the superior mesoporous characteristics and can be efficiently used for the air pollutant treatment process and the water treatment process.